Objection 1: It would seem that happiness consists in an operation of the senses also. For there is no more excellent operation in man than that of the senses, except the intellective operation. But in us the intellective operation depends on the sensitive: since "we cannot understand without a phantasm" (De Anima iii, 7). Therefore happiness consists in an operation of the senses also.
Obj. 2: Further, Boethius says (De Consol. iii) that happiness is "a state made perfect by the aggregate of all good things." But some goods are sensible, which we attain by the operation of the senses. Therefore it seems that the operation of the senses is needed for happiness.
Obj. 3: Further, happiness is the perfect good, as we find proved in Ethic. i, 7: which would not be true, were not man perfected thereby in all his parts. But some parts of the soul are perfected by sensitive operations. Therefore sensitive operation is required for happiness.
On the contrary, Irrational animals have the sensitive operation in common with us: but they have not happiness in common with us. Therefore happiness does not consist in a sensitive operation.
I answer that, A thing may belong to happiness in three ways: (1) essentially, (2) antecedently, (3) consequently. Now the operation of sense cannot belong to happiness essentially. For man's happiness consists essentially in his being united to the Uncreated Good, Which is his last end, as shown above (A. 1): to Which man cannot be united by an operation of his senses. Again, in like manner, because, as shown above (Q. 2, A. 5), man's happiness does not consist in goods of the body, which goods alone, however, we attain through the operation of the senses.
Nevertheless the operations of the senses can belong to happiness, both antecedently and consequently: antecedently, in respect of imperfect happiness, such as can be had in this life, since the operation of the intellect demands a previous operation of the sense; consequently, in that perfect happiness which we await in heaven; because at the resurrection, "from the very happiness of the soul," as Augustine says (Ep. ad Dioscor.) "the body and the bodily senses will receive a certain overflow, so as to be perfected in their operations"; a point which will be explained further on when we treat of the resurrection (Suppl. QQ. 82-85). But then the operation whereby man's mind is united to God will not depend on the senses.
Reply Obj. 1: This objection proves that the operation of the senses is required antecedently for imperfect happiness, such as can be had in this life.
Reply Obj. 2: Perfect happiness, such as the angels have, includes the aggregate of all good things, by being united to the universal source of all good; not that it requires each individual good. But in this imperfect happiness, we need the aggregate of those goods that suffice for the most perfect operation of this life.
Reply Obj. 3: In perfect happiness the entire man is perfected, in the lower part of his nature, by an overflow from the higher. But in the imperfect happiness of this life, it is otherwise; we advance from the perfection of the lower part to the perfection of the higher part.